We propose the following work for the coming year: a) Characterization of aminoglycoside resistance genes in Staphylococcus aureus; now that some of these plasmids have been introduced into B. subtilis we hope, by a combination of cloning and transduction, to confirm their nature as transposable elements. b) Studies of transposons encoding gentamicin and kanamycin resistance will continue, with special emphasis on the transposons that lack extensive inverted-repeated sequences. We wish to study the mechanism of transposition in these cases. c) The 3-N-acetyltransferase will be cloned, mapped and its DNA-sequence determined. This will provide information on the regulatory regions and in addition, sequences of point mutants should characterize the active site region. d) Studies of the plasmid and enzyme epidemiology of hospital outbreaks of resistant organisms will be continued.